As industrialization expands globally to include an ever enlarging list of countries, demand for oil as an energy source and as feedstock for the myriad of petroleum based products enjoyed by consumers necessarily increases. This demand puts pressure on high quality or readily obtainable oil supplies, and can result in shortages and cost increases. While additional lower quality oil reserves such as heavy oils and bitumen are in abundant supply in Canada, Venezuela and the United States, for example, they generally contain higher levels of high boiling components and/or higher concentrations of impurities such as sulfur, nitrogen or metals. The high boiling fractions typically have a high molecular weight and/or low hydrogen/carbon ratio, an example of which is a class of complex compounds collectively referred to as “asphaltenes”. Asphaltenes are difficult to process and commonly cause fouling of conventional catalysts and hydroprocessing equipment. These lower quality feedstocks are further characterized as including relatively high quantities of hydrocarbons that have a boiling point of 524 C. (975° F.) or higher. They are typically less attractive to oil producers because they require more expensive processing to break down the high boilers or remove or reduce impurities to acceptable commercial levels that would allow them to effectively compete with light crude. Other examples of lower quality feedstocks that contain relatively high concentrations of asphaltenes, sulfur, nitrogen and metals include bottom of the barrel and residuum left over from conventional refinery processes (collectively “heavy oil”).
Shortages and/or price increases in high quality oils help to level the playing field and compensate for any increased costs of heavy oil processing, permitting lower quality oil reserves to become attractive alternatives to light crude. To better compare to light crude, a refiner must modify a number of properties in heavy oils. In contrast to high quality oils, heavy oils and bitumen are typically characterized by having low specific gravities (0-18.degree. API), high viscosities (>100,000 cp), and high sulfur content (e.g., >5% by weight). Converting heavy oil into useful end products requires extensive processing, including reducing the boiling point of the heavy oil, increasing the hydrogen-to-carbon ratio, and/or removing impurities such as metals, sulfur, nitrogen and high carbon forming compounds. Langdon et al. (U.S. Pat. No. 7,712,528) describes certain heavy oil processing methods generally as well as identifies their shortcomings and the impact of high concentrations of asphaltenes on processing efficiencies.
Other processes reported to hydrocrack heavy oils include those disclosed by Lott et al. (U.S. Published Application No. 20110220553) that is said to disclose methods and systems for hydrocracking a heavy oil feedstock using an in situ colloidal or molecular catalyst. The invention reportedly involves methods and systems for hydroprocessing heavy oil feedstocks that include a significant quantity of asphaltenes and fractions boiling above 524° C. (975° F.) to yield lower boiling, higher quality materials and relate to ebullated bed hydroprocessing methods and systems that employ a colloidal or molecular catalyst and a porous supported catalyst.
To generally reduce the viscosity of oil, the industry has relied on various thermal and catalytic cracking processes. Pyrolysis, or “thermal cracking”, typically occurs when oil cracks at temperatures greater than about 650° F. Pyrolysis tends to improve certain heavy oil properties by reducing viscosity and API gravity but may also lead to increased content of acids. By its very nature, thermal cracking generally has minimal effect on total sulfur content. The result is a feedstock that is intrinsically less valuable to downstream processors. Moreover, the high temperatures required increase the likelihood of coke formation, which leads to fouling of refinery equipment or catalysts used by refiners to further process the oil into saleable products. Commercial solutions to these problems include carbon removal or hydrogenation, but costs for these processes must be borne by the refiners. A number of catalysts, including supported nickel catalysts, are available to hydrogenate or hydrotreat oils, but they are typically used in downstream processing. Improvements in nickel-based catalysts may lead to improved efficiencies in these downstream processes, thereby reducing costs and/or increasing product output. A number of processes to prepare certain supported catalysts for use in hydrotreating or hydrogenating various oils are known.
For example, one technique commonly used to obtain supported nickel catalysts starts with the nickel atoms dissolved in a solvent. The nickel atoms are usually provided as nickel salts due to the solubility of nickel salts in various solvents. The support material is added to the nickel solution and the nickel is then precipitated onto the support, typically by adding a base. The supported nickel catalyst is then dried and calcined (e.g., at 375° C.) and activated by reduction with hydrogen.
It is known in the art that heating and/or calcining the catalyst atoms causes agglomeration of catalyst particles to some degree. See Reyes et al., (U.S. Pat. No. 7,563,742). Agglomeration is undesired because it reduces the performance of the catalyst. Agglomerated particles have less exposed surface area and are consequently less active for a given amount of metal (i.e., only the exposed metal atoms on the surface are available for catalysis). Despite the undesirability of agglomeration, exposing the catalyst to heat is often necessary to activate the catalyst or for carrying out the reactions that involve the catalyst.
The extent of agglomeration during manufacture or use of the catalyst typically depends on the size and number of catalyst particles. Smaller particles are more likely to agglomerate because of higher surface tension as compared to larger particles. Higher metal loading also tends to facilitate agglomeration because the particles are in closer proximity. Although catalyst performance can in theory be increased with smaller catalyst particles, improvement in catalyst performance has been somewhat limited by the inability to beneficially increase metal loading while using small catalyst particles.
Reyes et al. (U.S. Pat. No. 7,563,742) discloses certain supported nickel nanocatalysts having high nickel loadings and methods for their preparation. These catalysts are reportedly useful, inter alia, for hydrocracking, hydrodesulfurization and other similar processes carried out in refinery settings.
Langdon et al. (U.S. Pat. No. 7,712,528) discloses some methods for dispersing nanocatalysts into petroleum bearing formations, forming lighter oil products within the formation, and extracting the lighter oil components from the formation. Processes for the in situ conversion and recovery of heavy crude oils and natural bitumens from subsurface formations are described therein.
Toledo Antonio, et al. (U.S. Pat. No. 7,981,275) reports certain catalytic compositions having a high specific activity in reactions involving hydroprocessing of light and intermediate petroleum fractions, and preferably in hydrodesulphurization and hydrodenitrogenation reactions, employing a catalyst containing at least one element of a non-noble metal from group VIII, at least one element from group VIB and, optionally, a group one element of the VA group, which are deposited on a catalytic support comprising of an inorganic metal oxide from group IVB.
Wong, et al. (U.S. Pat. No. 7,825,064) describes some catalytic materials, and more particularly, catalysts composed of metal oxide on which is supported another metal oxide wherein the support comprises nanometer-sized metal oxide particles.
Espinoza et al. (U.S. Pat. No. 7,323,100) discloses certain combination of amorphous materials for use in hydrocracking catalysts.
Park et al. (Published US Application No. 2011/0172417) describes some heterogeneous copper nanocatalysts and methods of their preparation composed of copper nanoparticles on boehmite.
Bhattacharyya et al. (Published US Application No. 2011/0306490) discloses certain compositions of supported molybdenum catalyst for converting heavy hydrocarbon feed into lighter hydrocarbon products. The support reported is boehmite or pseudo-boehmite and may further contain iron oxide.
Supported catalysts, especially nanocatalysts that maintain or improve catalytic cracking efficiency while requiring lower metal loadings, remain desirable yet elusive targets of the industry. Alternatives employing catalysts that could combine easier recovery of heavy oils from oil bearing formations and improve oil properties would be attractive to oil suppliers and refiners alike. Catalysts and methods of their use for hydroprocessing heavy oil feedstocks that include a significant quantity of asphaltenes and fractions boiling above 570° C. (1,058° F.) to yield lower boiling, higher quality materials are also desirable. Catalysts and methods of their use that, by their use in treat heavy oils in formation and recovery, extend the useful life of expensive equipment used to extract or further process the upgraded heavy oil fractions would be of commercial interest. The invention is related to these and other important ends.